1. Technical Field
The present invention relates to touch input devices. In particular, to opto-matrix frames having a minimum component count.
2. Background Art
Historically, keyboards were used to interact with display devices. Due to the needs of particular users, a number of alternative methods of interacting with display devices were developed. Included in the alternatives were items such as mice, light pens, tablets, joysticks, and the like. All of these methods have the disadvantage of requiring hardware extraneous to the display. The development of touch panel displays provided an alternative method of interacting with a display device which has the additional advantage of not requiring hardware extraneous to the display. Touch panel displays allow a user to interact by first presenting information on the screen. Then the user interacts by touching the screen at locations based on information displayed on the screen. The touch panel senses the location of the finger or stylus and communicates that information to the computer.
There are known alternative methods of designing touch panel displays. One method uses a transparent membrane switch which covers the surface of the display screen. Over time, the membrane design creates vision problems for the user. This is because the membrane lies directly over the screen. Therefore, membrane wear will have a direct effect on how well a user can see the display. A preferable method is the opto-matrix display. This type of touch panel display places nothing on the surface of the screen, eliminating the problems caused by membrane wear. Further, the frequency of energy used can be selected so that it is outside of the visible light range, thereby rendering the matrix invisible to the user.
However, a disadvantage associated with opto-matrix touch panel displays is the high component count and consequent high manufacturing expense. For example, a large number of light emitting diodes (emitters) are required to create the optical matrix. A correspondingly large number of detectors, paired with corresponding emitters, are required to detect light, or its absence, in the matrix. Further, scanning the emitters and monitoring the detectors typically requires significant on-board processing capability to scan the emitter/detector pairs, measure the difference between detector output before and after the emitter is turned on, and determine if a stylus is present at a given location. Touch panel displays also include digital to analog converters to allow data to be converted prior to being transferred to computers.
The prior art has failed to provide a touch panel input device that not only has the known advantages of opto-matrix displays, such as the absence of extraneous hardware, and the superior visual qualities of opto-matrix touch panels over membrane touch panel input devices, but one which also overcomes the disadvantages of known opto-matrix touch panel devices, which results in high cost primarily due to the number of components required to implement such a device.